Oil and gas wells are drilled into earth formations, first creating a borehole and then running and cementing casing in the borehole. Well tools such as bridge plugs, packers, cement retainers and frac plugs are often run into cased wells and set in casing to seal sections of wells. Conventional well tools providing well casing sealing assemblies typically comprise a packer having one or more elastomeric sealing elements which are squeezed between a packer mandrel and the casing, and held in place by one or more slip assemblies which are wedged between conical sleeves of the packers and the casing. The packers are configured for use as bridge plugs, tubing packers, cement retainers, and frac plugs. The packer mandrels provide a central body on which various components are mounted. The mandrel is attached to a stationary portion of the setting tool and held in a fixed position, and the setting sleeve typically extends around the mandrel and is stroked downward against an uppermost sleeve of the well tool being set. The upper sleeve will then move downward toward a lower end of the mandrel, pushing anchor slips over conical elements and compressing an elastomeric seal element between the mandrel and the casing. During setting of the casing seal device, shear pins will be sheared to release the setting tool from the set well tool so that the setting tool may be retrieved from the well and be redressed for repeated later use. U.S. Pat. No. 3,082,824, invented by F. A. Taylor et al and issued Mar. 26, 1963 shows use of a machined weak point to connect a setting rod to the lower end of a well tool mandrel, with the weak point releasing when the well tool is set to release the setting rod and firing head from the well tool.
Modern frac plugs are used for sealing sections of well casing and selectively applying pressure to multiple formation production zones for sequentially pumping treatment fluids and frac proppants into the various formations. After treatment, the frac plugs are often drilled out so that fluids produced from the treated production zones can be produced from the well. Conventional frac plugs are made of cast iron and composite materials which are more easily and more rapidly drilled than plugs made of steel. Recently developed frac plugs are made of materials which dissolve when exposed to time, temperature and fluids in the well, avoiding drill-out. Frac plugs and packers often have an upper end which is formed to provide a ball seat for sealingly engaging with drop balls. Drop balls are often dissolvable and include dissolvable frac balls which are dropped onto the ball seats. After well treatment at a zone above a particular frac plug, the frac ball will dissolve after exposure to time, temperature and fluids in the well, and fluids may be produced from lower production zones through the central bore in the frac plug without the need to drill-out the frac plug.
Frac plugs have been set with tubing and with gas powered setting tools. Conventional gas powered setting tools have power charge chambers in which power charges formed of flammable solids are burned to generate pressurized gases which move one or more pistons to forcibly set the well tool being run within the well. One such setting tool is shown in U.S. Pat. No. 2,618,343 issued to Martin B. Conrad on Nov. 18, 1952. Conventional setting tools use hydraulic oil located between a first piston disposed in a first cylinder and a second piston disposed in a second cylinder. The first piston in the first cylinder is pushed directly by power charge gases and in turn pushes the hydraulic fluid, which then pushes the second piston in the second cylinder. The second piston is then typically connected by a rod and linkage to a setting sleeve for pushing against and setting the well tool in the casing. Recently a disposable setting tool was developed in which the flammable solids are used for stroking the setting tool, without use of hydraulic fluids, as shown in U.S. Pat. No. 9,810,035, invented by Jimmy L. Carr et al., and issued to Diamondback Industries, Inc. on Nov. 7, 2017. The prior art has also included bridge plugs in which a setting tool is built into the bridge plug, such as U.S. Pat. No. 7,017,672 which was invented by Harrold D. Owen, Sr., and issued on Mar. 28, 2006.